A number of compounds which catalyze a hydrogenation reaction are known (refer to SHIN JIKKEN KAGAKU KOZA 15, SANKA TO KANGEN (II), Maruzen (1977)). These catalysts can be roughly divided into homogeneous catalysts and heterogeneous catalysts.
In heterogeneous hydrogenation reaction, a reactant is generally used in a gaseous phase, and applicable reaction substances are therefore limited. Besides, since high reaction temperature are required, the reaction substance is apt to decompose thus producing by-products. Further, heterogeneous catalysts for hydrogenation have lower selectivity than homogeneous catalysts for hydrogenation.
On the other hand, catalysts comprising the group VIII transition metals, such as rhodium, platinum, and ruthenium, are well known for homogeneous hydrogenation, but these metals are extremely expensive and therefore economically disadvantageous.
In addition, the above-mentioned catalysts are disadvantageous in that they not only catalyze hydrogenation but induce hydrogenolysis of a carbon-halogen bond, etc.
In order to overcome these disadvantages, there have been proposed complexes of the group VIB metals, e.g., chromium, molybdenum, and tungsten, such as arenechromium tricarbonyl and bis(tricarbonylcyclopentadienylchromium). However, these complexes exhibit activity only on hydrogenation of cissoid dienes or acetylenes. Moreover, they must be used in a large quantity due to their low catalyst activity and still require high temperature and high pressure conditions for accomplishing the desired reaction. Thus, there are great difficulties in applying these complexes to industrial use (see Comparative Examples 1 to 5 hereinafter described).
Silyl ethers, allyl silanes, and vinyl silanes are all very important key substances in industry (see, for example, W. P. Weber, Silicon Reagents for Organic Synthesis, Springer-Verlag (1983)).
Conventionally known catalysts and processes for directly producing silyl enol ethers from carbonyl compounds and hydrosilanes include (1) a process comprising reacting a hydrosilane with a carbonyl compound having an electron attracting group at the .alpha.-position thereof, e.g., acetylacetone and methyl aceto-acetate, using a Wilkinson complex (Rh(PPh.sub.3).sub.3 Cl) as a catalyst (see I. Ojima, M. Nihonyanagi, T. Kogure, M. Kumagai, S. Horiuchi, and K. Nakatsugawa, J. Organomet. Chem., Vol. 94, p. 449 (1975)) and (2) a process comprising reacting cyclohexanone and trimethylsilane using triethylamine as a base and cobalt octacarbonyl as a catalyst (see, H. Sakurai, K. Miyoshi, and Y. Nakadaira, Tetrahedron Lett., 2671 (1977)).
According to the former process using a Wilkinson complex as a catalyst, it is essential for selective progress of dehydrosilylation that the substrate should have an electron attracting group at the .alpha.-position thereof, thus narrowly limiting the applicable substrate in kind. The latter process also has a disadvantage such that a substrate to be used must be chosen taking into consideration side reactions arising from the co-existing strong base, e.g., aldol condensation. Further, both reactions are economically disadvantageous because of the use of complexes of expensive metals of the group VIII and entail great difficulties in industrial application (see Reference Examples hereinafter described).
Known catalysts and processes for directly producing allyl silanes from dienes and hydrosilanes include a process in which a complex of the group VIII transition metal, e.g., platinum, palladium, and rhodium, is used and a process utilizing an photochemical reaction with the aid of a chromium hexacarbonyl catalyst (refer, e.g., to S. Patai and Z. Pappoport (ed.), The Chemistry of Organic Silicon Compounds (1989)). Reactions using these catalysts, however, are often attended by by-production of a homoallyl silane as a result of progress of 1,2-addition reaction or of a disilylalkane as a result of 1:2 addition reaction, thereby giving a complicated mixture. In using assymetric dienes, these catalysts are hardly applicable t industrial production because the resulting reaction mixture contains positional isomers. Further, uneconomic to use expensive group VIII metal complexes as a catalyst and to use an apparatus for photochemical reaction, making it difficult to adopt these reactions from the standpoint of economy.
Known catalysts and processes for directly producing vinyl silanes from acetylenes and hydrosilanes include a process of using a complex catalyst of the group VIII transition metal, e.g., platinum, palladium, and rhodium, similarly to the above-described processes for producing allyl silanes (see, for example, The Chemistry of Organic Silicon Compounds, supra). Where these catalysts are used, the resulting vinyl silane products are mixtures of stereo isomers sometimes containing a disilylalkane that is a 1:2 addition product, thereby providing complicated mixtures. In the case of using assymetic acetylenes, the resulting mixture further contains positional isomers. Therefore, these processes are unsuitable for industrial application.